The invention relates to a thread cutting device for a chain stitch sewing machine.
A thread cutting device in accordance with U.S. Pat. No. 4,098,209 has three guideways in the form of slots which cooperate with further guide parts in such a way that a thread catcher is moved towards a catching position parallel to the back of a looper and beyond a knife restrained by means of a stop and from there back into an inoperative position adjacent to the path of movement of the looper. The construction of these guideways is expensive and might lead to premature wear on the guides.
A further thread cutting device is known from U.S. Pat. No. 4,726,305 in which guides make a similar path of movement of the thread catcher possible. In this case, the transition of the path of movement of the thread catcher from the arcuate to the linear phase is effected abruptly, and might also lead to premature wear on the guides or to undesired vibration of the thread catcher.
The JP Utility Model Hei 2-126578 discloses a further embodiment of a thread cutting device. Here also, the transition of the path of movement of the thread catcher from the arcuate to the linear phase is abrupt. This might also lead to undesired vibration of the thread catcher.
Thus, an object of the invention is to develop a thread cutting device in such a way that the path of movement of the thread catcher into the catching position and back into the cutting position and then into the inoperative position is as smooth as possible.